text:
Barometric altimeter data during high vertical g-forces?
I’m contemplating that that under high vertical acceleration (such as the maximum limit of 2.5g for commercial airplanes), that hydrostatic atmospheric pressure wouldn’t be a complete model. Wikipedia states for atmospheric pressure:

In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point.

The derivation of the Barometric formula presumes hydrostatic pressure:

And assuming that all pressure is hydrostatic:
  dP=-ρgdz

It appears to me that without correction for the g-forces, a vertically accelerating barometric altimeter could potentially indicate uncorrected altitudes which are lower or higher (depending on the design of the altimeter) than true altitude even if all other factors had been corrected.
Is this a correct understanding and do Air Data Computers (ADC) described below make these corrections? If yes, can anyone provide an approximate formula or mathematical model for altitudes near ground level?
Another Aviation Stackexchange answer states:

However, altitude is also used for the purpose of traffic separation, and for this purpose, neither QNH or QNE is corrected. This might sound counter-intuitive, but as long as your altimeter is showing the same error as any conflicting traffic, you can be safely separated, therefore: The altitude shown on the altimeter is not corrected at all (except by calibration for possible aerodynamic interference, such as compressibility, venturi-effects etc).
In technically sophisticated aircraft, barometric altitude input is used for vertical navigation. Since vertical navigation is concerned with the true altitude of the aircraft, the aircrafts Air Data Computer (ADC) will calculated a true altitude based on information available to it (either through sensors, or through pilot input). The true altitude is however, as stated, not shown on the pilots primary flight instruments.

In the formula $dP = -\rho gdz$, $g$ is the local gravitational field that is pulling on the fluid (the atmosphere).  The apparent value of $g$ within the airplane is not relevant.
So other than making sure the sensor itself isn't affected by changes in apparent weight, there's no need to correct for accelerations of the barometer.

And yes I am intending to ask whether the sensors are designed such that their “apparent weight” (or more generally their mass acted on by any directed force) is not an appreciable factor in their reported measurements?

My understanding is that no, it's not.  Altimeters already have a measurement error at level flight, and they have a lag when altitude is changing.  Additional errors due to apparent weight would have to exceed those to be worrisome.
"vertical acceleration" is rather small for almost everything that's not a military fighter.  But a plane could easily pull 3g's in a level turn, and you would want your altimeter to remain accurate.
Obviously it's possible to design an instrument that is more susceptible to such inaccuracy (such as have the pressure vessel balance against a weight to indicate the altitude), but that shouldn't be a problem for a normal instrument.
The aneroids in a diaphragm barometer can be oriented so that downward forces have no effect on the reading.  Also, the smaller and lighter the disks, the less that any acceleration will affect the reading.
I found lots of articles on various corrections for barometric altimeter readings based on temperature and different atmospheric profiles, but none on g-load corrections.  That suggests to me that no correction is necessary for standard instruments.  Perhaps someone can find published performance data for an installed instrument that calls it out explicitly.  The lack of information I found appears reasonable, but not completely satisfying.

I don’t remember much about fluid physics. Why is that the forces of the physical devices of the barometer on the fluid haven’t increased? Perhaps I’m not understanding well enough how said devices measure the pressure. I guess I was assuming they’re like a balloon filled with some gas so the relative pressure of the atmosphere outside the said balloon is resisting the expansion of the balloon by the pressure inside the balloon. Increase in pressure on one side of the balloon would I posit be offset by a decrease on the other side. Would altimeters necessarily be unaffected by such asymmetry?

To clarify further, I (at least now do) understand that the hydrostatic pressure is a macro effect of the atmospheric fluid (gas) which is largely at rest (and earth’s gravity largely at rest) relative to the movement of the altimeter. So the g-forces can’t impact the macro hydrostatic pressure. I failed to make it clear in my question that I’m contemplating whether there are forces generated within the barometer under dynamic conditions which have to be corrected for? I suppose ideally the barometer should be unaffected by such forces, but is this actually the case?

And yes I am intending to ask whether the sensors are designed such that their “apparent weight” (or more generally their mass acted on by any directed force) is not an appreciable factor in their reported measurements? And specifically for example for altimeters designed for aircraft that are not (in normal use) supposed to experience significant upward acceleration g-forces.

Thanks for your edits and sharing your knowledge.


text:
What is the commercial passenger aircraft top speed record?
Aircraft manufacturers claim that commercial passenger aircrafts cruise at the speed of 400-500 knots.
But, is the top speed of a commercial passenger aircraft recorded (while in air)? If so, what is the top speed?

You may precise if you exclude the Concorde. Including it seems unfair.

@Gokul Nath KP you need to define whether or not your definition of top speed is for level flight under power, or in a dive with gravity helping.  Veritible ASE lives are in the balance...

Concorde/TU-144 absolutely should be recorded. (Tu-144 may have been a few knots faster).  Surprised Virgin Galactic doesn't add 2-3 Concordes to their portfolio, but their Spaceship 2 will soon take the title.  Great story about the DC-8 below.

@RobertDiGiovanni Virgin tried to shame BA into selling (read: giving) their Concordes to Virgin Atlantic rather than retire them, but it was all a Branson PR stunt because he had utterly no intention of carrying through with the request (he also knew that Airbus had withdrawn the type certificate, so they couldn't fly again - Airbus was no longer supporting them).

Rules and paperwork shut down a great plane, then they tried to build the A380.  In this day and age an internet marketing survey may have them asking for the Concorde.

@JohnK To be exact, we need to specify whether we need direct witnesses, or whether radar and a FDR is enough.

In case any reader is wondering about Concorde, Wikipedia gives its cruising speed as "Mach 2.02 (2,150 km/h; 1,330 mph)". Wikipedia says the TU-144 " cruised at a speed of around 2,000 kilometres per hour (1,200 mph) (Mach 1.6)."

air speed or ground speed?  because i would imagine that when flying with an opportune jet stream it might be possible to have a ground speed greater than mach 1 without actually breaking the speed of sound.

@RedGrittyBrick Yea, I wouldn't trust the wiki on those numbers. We'd need to check Tech sheets or actual observations.

@Michael Mach number is based on the local speed of sound, and therefore affected by altitude and other conditions. By definition, if you are travelling at Mach 1, you are travelling at the speed of sound in your local environment. You can't divorce "Mach 1" from the local environment without specifying the environment, and then you're no longer talking about the same thing.

If Commercial Crew happens this year as has been promised (though they've been saying that for several years now...), this question might be better off in Space Exploration.SE.  SpaceX and Blue Origin are both pretty close to being able to fly passengers at orbital velocities, and could technically count as "commercial aircraft".

@RobertDiGiovanni in "this day and age" lip-service to rules and paper work gave us the B787 battery fires and the B737MAX.  Thankfully, not all aircraft are manufactured in a country where "federal regulations" can be a covert synonym for "industrial protectionism". Nobody needs another preventable AF 4590 disaster just because the plane looked cool.

@alephzero "this day and age" means more technology (tools) are available, but it won't help if you can't cook.  This is why people working together and communicating properly remains critical. With cheap fuel, metrics have changed, and that good ol' supersonic delta won't need MCAS.

"Speed" is not a singular term in aviation. There are many different ways to measure speed. See for example Why is there a difference between GPS Speed and Indicator speed? Most commercial jets cruise with a true airspeed in the range 400-500 knots and an indicated airspeed in the range 200-300 knots.
For the purpose of passenger transportation, ground speed is interesting since it is a determining factor in how long it takes to get from A to B. But do note that ground speed has relatively little to do with aircraft performance, since two identical aircraft could have vastly different ground speeds if one was flying in a headwind and the other in a tailwind.
According to groundspeedrecords.com, the fastest ground speed ever recorded for a commercial aircraft is the Concorde with a record of 1205 knots. This website relies on pilots snapping a picture and uploading it to the site as proof, so it is possible that that record has been broken without it being recorded.
Excluding the Concorde, which is no longer in service, the fastest record is a Boeing 747-400 recorded at 752 knots in 2010. At the time of reaching that speed, the aircraft had a 213 knot tailwind (probably flying in a jetstream).

I wonder if that site has any record of the 747 which went supersonic during an incident....

fyi 1205 knots is 2232 km/h (Concorde), or Mach 1.81.

@RingØ You can't convert groundspeed to mach though

@Moo Supersonic is a flow regime - it's entirely relative to the air, so a tailwind cannot make a subsonic aircraft suddenly become supersonic.

@J... I’m not talking about a tailwind, I’m talking about a cargo 747 that suffered an inflight incident causing it to dive uncontrolled and vastly exceed its maximum operating speed.

@Moo  You don't mean this flight?  It was reported (speculated!) to have gone supersonic, but the final report seems to state it had hit a max speed of M0.98.  Lost a couple of wing panels and one of the flaps fell off during (after?) landing.

@J.Hougaard Oh ok, didn't know that. So Mach is not the ground speed, it's the actual speed? In this case, wouldn't the actual speed be more relevant then (which is always higher than the ground speed)?

I once measured an average of 1000 kph on the way from USA to Europe.  That’s more than 500 knots, but it’s ground speed.

Wow great answer!

@RingØ Mach number is based on airspeed. Also, the airspeed-to-Mach-number  conversion varies with altitude and atmospheric conditions. Mach 1 is always the speed of sound through the medium in question, but that speed can vary quite a bit depending on the medium.

As an indication, https://upload.wikimedia.org/wikipedia/commons/9/9d/Comparison_US_standard_atmosphere_1962.svg this is the mach number versus the height in the standard atmosphere.

@RingØ There is no such thing as "actual" speed, there is airspeed and ground speed. And airspeed can be either higher or lower than groundspeed.

@GlenYates There is this page that explains how AS can be lower than GS (due to the definition of airspeed)

@e2-e4 - The page in your link gives an example of the correlation of airspeed to ground speed. In practical, real world use, either airspeed or groundspeed can be higher or lower than the other, as Glen Yates said. It all depends on the direction of air movement. Do you have a headwind or a tailwind. Also, There are 5 different types of airspeed if you include Mach speed (not usually done due to it being a ratio of air speeds).

Other than the TU-144 and Concorde, the record for the fastest True Airspeed in an airliner probably belongs to a DC-8.
Wikipedia Douglas DC-8

On August 21, 1961, a Douglas DC-8 broke the sound barrier at Mach 1.012 (660 mph/1,062 km/h) while in a controlled dive through 41,000 feet (12,497 m) and maintained that speed for 16 seconds. The flight was to collect data on a new leading-edge design for the wing, and while doing so, the DC-8 became the first civilian jet – and the first jet airliner – to make a supersonic flight. The aircraft was DC-8-43 registered CF-CPG later delivered to Canadian Pacific Air Lines. The aircraft, crewed by Captain William Magruder, First Officer Paul Patten, Flight Engineer Joseph Tomich and Flight Test Engineer Richard Edwards, took off from Edwards Air Force Base in California, and was accompanied to altitude by an F-104 Starfighter supersonic chase aircraft flown by Chuck Yeager.

Douglas DC-8-43 N9604Z is accompanied by a U.S. Air Force Lockheed F-104A Starfighter, near Edwards Air Force Base, California. (Douglas Aircraft Co.)

Hey that's not level flight, that's cheating lol.  But still holy crap that's impressive.  We'll need the poster to clarify if he means absolute speed or level flight speed to settle this "shock(wave)ing" situation.

The captain should have has a shirt made, reading "Chuck Yeager is my chase pilot"

The 747 also went supersonic on a few occasions. I bet Terry could give more detail.

I didn't realize such planes could even survive the stresses of supersonic speed. Impressive.

I think I know what you're asking, and the Concorde-excluded answer is almost certianly the Convair 990 which could get just shy of Mach 1.  From wikipedia:

The Convair 990A is still the fastest non-supersonic commercial transport to have ever been produced. During May 1961, one of the pre-production 990 prototype aircraft set a record of .97 Mach in level flight at an altitude of 22,500 ft. (6.9 km), equivalent to a true airspeed of 675 mph (1 086 km/h).[5] This was before the various aerodynamic drag-reduction changes were applied to the later 990A in order to meet certain performance guarantees which Convair had made to American Airlines. These subsequent modifications made to the later 990A (consisting of the four wing-mounted anti-shock body "speed capsules" and substantial streamlining of the engine pylon/wing interface) increased the velocity at which onset of transonic drag would occur by 0.09 Mach. As such, the 990A would have been capable of speeds slightly in excess of 700 mph (1 130 km/h).[6]

If the fastest crossing of the Atlantic is your metric, the winner is the Vickers VC-10. It was very advanced for its time with airfoils close to what today would be called supercritical. In 1979, Super VC-10 G-ASGC took off from JFK to land just five hours and one minute later at Prestwick. The scheduled time was six hours and twenty minutes. This record has never been beaten to this day by a scheduled aircraft.
Of curse, it helped that ground control was supportive. As Captain Gwyn Mullet describes in his autobiography:

… so I asked what the record was for the route and they ferreted around and said that it was held by a 707 at five hours and eight minutes. My tail was up and so I put a little bit of extra fuel on and told the people that we were out to beat that time. Little did I know that they informed the control tower and so just after take-off we were told to route direct to Gander, Newfoundland and to ignore any speed restraints and they wished us good luck in our venture.
“Wow, we are off and running!” I said to the rest of the crew triumphantly.
After about two hours or so we were in the Gander area and we called for our ‘Atlantic clearance’ and would you believe it they were in the picture as well. They told to route direct to Prestwick and not on the normal track system. As for the speed we were given a free hand as to how fast to go.

The maximum operating speed of the VC-10 was Mach 0.886 or 505 kts.

Nautically at that speed takes four hours. Scheduled for six, it took one more hour than what's physically possible.

@Mazura By "Nautically" do you mean, if you fly a Great Circle route JFK-PIK? In 1979 (pre-GPS), would that have been possible? You'd have to continually adjust your bearing, but how would you know your position to sufficient accuracy? Is that what he means by the comment about flying direct? Can I only ask questions?

@Mazura The Great Circle from JFK-LHR is 2999NM and at 505 Knots would take  6:50. They obviously had to rely on a tailwind. What do you mean "physically possible"?  http://www.gcmap.com/mapui?P=jfk-lhr&PM=b%3Adisc10%2B%22%25N%2220&MS=wls&DU=nm&SG=505&SU=mph

Most of the fastest airliners are limited by the speed of sound, and their speeds (actually Mach numbers) are within a narrow range so the values are quite similar. This is because the aerodynamics of a transonic airplane will create various instabilities and stalls near the sound speed limit where the local flow at the wing is already locally supersonic. The drag will also be high.
There is also an indicated airspeed limit, but at cruising altitude the indicated airspeed is not high due to low air pressure (and density).
The maximum operating Mach numbers (Mmo) are like these: 747-400 has one of the highest values: 0.92; VC10 has been reported even as 0.94, but I do not know if it is reliable; DC-10 0.88.  B737 and A320 are much lower at 0.82.
The aircraft are allowed to reach slightly higher values, but not by much: the overspeed sound may sound already at Mmo.

And this just in: In Peter Kämpf's answer he presented Atlantic crossing as one of the metrics, and the age-old Vickers VC-10 record has been beaten.
The new subsonic Atlantic crossing record (this time New York JFK to London LHR) stands at 4 hours and 56 minutes. A staggering 80 minute gain en route!
BBC: Storm Ciara helps plane beat transatlantic flight record

The Boeing 747-436 reached speeds of 825 mph (1,327 km/h) as it rode a jet stream accelerated by Storm Ciara.
The four hours and 56 minutes flight arrived at Heathrow Airport 80 minutes ahead of schedule on Sunday morning

It was a British Airways flight and it impressively shows why their callsign is Speedbird.

But it was storm „Sabine“

@pcfreakxx In Germany it's called "Sabine", in the UK (and probably elsewhere) it is called "Ciara".

@PerlDuck Oh M8

80 minutes ahead of schedule but only 5 minutes faster than the Vicky.

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How to compare turboprop engines and with which values?
I have found this website that lists a lot of turboprop engines. I would like to compare them with as few values as possible. As an example, there are tons of different values that describe a jet engine, but the most important/significant values are thrust and bypass ratio. Out of the many different values for a turboprop engine, which would be the few most important/significant to include?
My goal with the data is to approximate (very roughly) comparative fuel usage.
EDIT: To clarify the question, what are the most important engine values/specifications that can be used to estimate the general fuel economy of the turboprop engine?

The main problem I see in this list is that it does not differentiate between turboprops and turboshafts.

That's good to know, thank you. Is there a big difference performance-wise? I might add that I'm not interested in helicopters and such

Are you planning to design one into an airplane?

The idea is to estimate fuel usage of one aircraft compared to another aircraft. It doesn't have to be actual litres/minute, but more along the lines of "aircraft A uses 1.5x more than aircraft B". The engine performance plays a big role in determining fuel usage, e.g. a turbojet uses more fuel per thrust than a turbofan regardless of aircraft it is mounted on.

@DeepSpace. A turboshaft and a turboprop both provide shaft power. There is no difference.

@Penguin but can they be compared using the same criteria?

@DeepSpace. Yes. Typically, a turboshaft drives a helicopter rotor, a turboprop drives a propeller. But, a rotor is just a prop mounted horizontally. Both engines provide shaft power. They cannot tell what they are rotating, which is really the same, anyway.

This database covers turboshaft and turboprop engines. Typically, the key factors one would use to compare such engines are:

SFC: Specific fuel consumption. This is how many kg/s (or lb/s) of fuel the engine consumes to produce 1 kW (or 1 hp). To calculate the SFC, divide the fuel flow at a throttle position by the amount of shaft power produced at that throttle setting. SFC decreases as overall pressure ratio increases. A low SFC means a more fuel efficient engine.
Specific power. This is, how much shaft power (kW) is produced per kg of air ingested by the engine. To calculate this, divide the shaft power by the air mass flow. A high specific power means you can get the power you need from a smaller, and hence lighter engine. A higher figure occurs when the engine has a high turbine temperature, and aerodynamically efficient compressors and turbines.
Power to weight ratio. To calculate this, divide the shaft power produced by the engine weight. As above, a higher figure occurs when the engine has a high turbine temperature, and aerodynamically efficient compressors and turbines.

Specific power is dependant on the properties of the propeller, yes? Since we are talking turboprops

@MatiasLq.  No, specific power is purely a performance metric about the engine. It’s the shaft power provided by the engine (to the prop), divided by the air ingested by the engine. The efficiency of the propeller is a completely separate metric, that describes how well the prop turns that shaft power into thrust.

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How does the F-35 hover?

The picture shows the aircraft hovering; how does it do that?

Because it's got one of these ?

@AakashM doesn't it also have thrust vectoring at the rear?

@Notts90 that's one of the parts of the LiftSystem

What prevented you from looking up F-35 on Wikipedia? (Or some other source on the internet). Here's a link to section of the B-(STOVL-)variant:  https://en.wikipedia.org/wiki/Lockheed_Martin_F-35_Lightning_II#F-35B . Or what is your specific question not answered in this section?

@Scrontch A group of people with common interest, passions, knowledge and experience got together and created an online forum where other people could come and ask questions. Now imagine we are all gathered in a bar and invited people to come along.  You've just done the equivalent of then telling them to go away because they can find the answer somewhere else. This is not a close reason, nor is it a reason to reject a question.  If it where, half the questions and answers on here would not exist.

Similar to this question

@Simon: Fair point. That being said, i think it's also considered good netiquette in any internet community when the asker somehow proves to show that he's invested say 5 mins on researching the topic himself before asking. I failed to see that being the case here.

The F-35 has what is called the Rolls-Royce LiftSystem. This Contains one lift fan in the middle of the aircraft, and a rotating jet exhaust to provide vertical thrust, and two rotating nozzles to provide stability. The pilot pushes a button, and doors on the aircraft open for the lift fan, while the exhaust nozzle rotates downward.
The pilot controls the thrust and pitch/roll, while a computer double checks what he does to maintain stability.
Here is a good video of it in action and here is a video that has a nice animation of it working.

Actually, the picture above is USMC (US Marine Corps),s F-35B, which he have a STOVL (Short Take-Off and Vertical Landing) capability. That aircraft hovers using a Rolls-Royce Allison fan to lift itself. The Rolls-Royce Lift System works like this image: The lifting system itself moved by the F-35's engine. The pilot works at the pitch of the fan, meanwhile computer countermeasures how to maintain stability. The pilot itself could push a button or use voice-activating system to open the lift-fan's door.

Hi.  Please edit your answer to include the attribution for the image.

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Apart from Kenya, what are the current dangerous / unsafe airspaces?
Notams are regularly released to warn about unsafe areas, e.g. Kenya:

A0040/15
  - SECURITY .. UNITED STATES OF AMERICA ADVISORY TO U.S. OPERATORS
  CONCERNING POSSIBLE ATTACKS WITH MAN - PORTABLE AIR DEFENSE SYSTEMS
  (MANPADS)
ATTENTION U.S. OPERATORS: INFORMATION INDICATES THE POTENTIAL FOR
  TERRORIST ATTACK AGAINST U.S. AND WESTERN INTERESTS IN KENYA.
  WHILE SPECIFIC DETAILS ARE NOT AVAILABLE, ONE POSSIBLE TACTIC WOULD
  BE AN ATTACK USING MAN - PORTABLE AIR DEFENSE SYSTEMS (MANPADS),
  SUCH AS THOSE USED AGAINST AN ISRAELI AIR CARRIER DEPARTING FROM MOMBASA,
  KENYA ON NOVEMBER 28, 2002.
  THE DEPARTMENT OF STATE HAS ISSUED A TRAVEL WARNING FOR KENYA REGARDING
  TERRORIST ATTACKS.

Is there a list of these hazardous airspaces, or a site than can be checked without searching in Notams from around the world? Is there a ranking of the hazards?

I feel there is more to say than currently answered, feel free to reuse part or all of this content to build an improved answer which could be selected.

There are recaps of flight restrictions, e.g. French DGAC publishes maps and plain text files recapitulating areas, in addition of individual NOTAMS:

Source: DGAC
ICAO announced in 2015 the creation of a specific member-collaborative tool CZRI, conflict zones risk information (currently very poor).
EASA also publishes a list of conflict zones bulletins that can be exported as pdf, and a map:

There are also other initiatives, e.g. SafeAirspace with text summary and maps. "SafeAirspace is managed by Flight Service Bureau, with contributions from The Airline Cooperative (225 international airlines), OpsGroup (1500 members), International Ops Bulletin feedback (40,000 readers), and data from the German BMVI, the UK DFT, the FAA, DGAC France, ICAO, and EASA."

You should always check NOTAMs when you fly. It is a must for safe operation.
However if you are just interested in hot spots on international scale you can check https://www.faa.gov/air_traffic/publications/us_restrictions/
It provide many interesting informations about worldwide hotspot in the eyes of FAA.
For local hotspot try: http://tfr.faa.gov/tfr2/list.html

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text:
Has Airbus planned to build a larger version of the A380?
The current Airbus A380-800 could carry over 800 people. Has Airbus planned to build a new, larger version that could carry 1000 or more passengers?

Welcome to the site! Unfortunately I'm not sure what you're asking and it looks like it will be difficult to give a precise answer because I guess no one outside Airbus knows for sure what their plans are and Airbus employees probably wouldn't discuss them anyway. I suggest that you try to ask a more specific question that can be answered clearly or, if you simply want to discuss this topic then the chat room would be a better place.

thanks a lot for your response!! My quetion is about if they have planed to build more high capacity versions

OK, that's helpful. I've edited the question to make it more specific; if you don't like the edit then you can just change it back.

Has Airbus planned to build a larger version of the A380?

Yes,
In 2012 they planned to build a larger version of the A380.
"Airbus says 1,000 seat A380 due 2020"
However, manufacturers do change plans from time to time, sometimes in response to market conditions. "Has planned" is not necessarily the same as "is planning". Those plans are not currently (8 Jan 2015) being pursued and consequently, as time goes by without a resumption of those plans, it is increasingly likely that any target dates in those plans may no longer be attained.
If you want to know do Airbus in January 2015 have active plans to build a larger version of the A380 - that would be a new question.

That article says that the project was shelved in 2010. Given the soft sales figures since the article was written and that they are not taking orders for a -900 as of today, I'd guess than a 2020 date is unlikely.

The question was whether Airbus has planned a larger version. They have but, as you noted, plans change. @reirab. I'll update the answer to make this plain.

The answer is clearly yes: The ratio of wingspan to fuselage length is unusually large for modern transport aircraft. The A380 has a wingspan of almost 80m and a fuselage length of less than 73m, whereas in other modern transport aircraft the fuselage is longer than the wingspan is wide.
Airbus designed the A380 with lots of stretch potential. With the cooperation of engine manufacturers, the A380 may one day have a fuselage length of around 100m. This is greater than the maximum length of 80m used in current airport layouts, but Airbus is betting on operators to urge airports to accomodate a stretched A380, just like they did for the current model's wingspan, weight and height.
The A380 will be the biggest Airbus for the next 30 or maybe even 50 years, so it better offers some growth potential.

The odd proportion of wings to fuselage is also caused by the double-deck layout: due to the high weight, the A380 needs a lot of lift.

Airbus has certainly made preliminary plans for a stretched version of the A380 (the A380-900,) but no plans currently exist for that model to go into production. Demand for the A380 has been soft, leading Airbus' own CFO to suggest to investors last month that the A380 might be discontinued entirely unless they can find enough customers willing to buy a re-engined version of it soon.
Orders for large, quad-engine airliners, including the A380, have been light lately. Since taking the first order 14 years ago and over 7 years since the first delivery, only 318 A380s have been ordered, nearly half of which were from Emirates, and many of the A380's orders will likely be cancelled. While the Boeing 747 has had over 1,500 deliveries over its long lifespan, it, too, currently has a small order book with only 16 net new orders since 2008. In contrast, twin-engine wide-bodies have been selling very well lately. The A350 just delivered its first aircraft and already has 778 orders. Similarly, the first 787 was delivered a little over 3 years ago and it has 1,055 total orders, so far. The 777X, currently scheduled for production in 2020, was first offered for order a little over a year ago and already has 286 orders. Total 777 orders so far number a whooping 1,807. The long-haul wide-body market has been trending very strongly towards twin-engine aircraft like the 777, A330, 787, and A350 lately rather than mammoth quad-engine aircraft like the 747 and A380. As such, it seems unlikely that Airbus is going to be sinking billions of dollars into a stretched A380 any time soon.

Actually I think they don´t have any plans for a stretched version of A380.
Tim Clark, CEO of Emirates, wants a larger A380 but Airbus said (last time when this topic came up) that they would rather improve the current A380 and increase the performance.
They are making a change by increase the lower floor height to add extra seat in each row
on economy but thats it.
Now Tim Clark is pressuring to make a neo-version af A380 and and Airbus is considering
that option. Emirates say that they would order up to 70 A380neo if that plane will be launched but Airbus has to calculate the cost and if it´s will be profitable for them.

Welcome to aviation.SE Ingdor (sorry, my keyboard doesn't support Icelandic :-)) "I think" doesn't really qualify as an answer here. We'd like to see your thoughts supported by evidence. Any links perhaps that support your claims?

Hi, Delta Lima
Airbus talked about strecthing the A380 back in 2012 with seats for 100 more passengers but
because of poor demands Airbus said in june 2013 that they would improve the current version instead
Here´s link to a story I wrote on my website (sorry it´s in icelandic but google translate should do the trick)
http://www.alltumflug.is/flugfrettir/4108/Ekki_%C3%AD_myndinni_a%C3%B0_lengja_A380
But it´s interesting maybe to know the status if there are any plans to make A380-900. I´ll contact Airbus spokesman
after the weekend and get the lates info on that

Of course they have plans to stretch the A-380! They had them before starting the project. That they now claim not to have any is probably to make airlines buy the current model.

If you have a reference for a quote from Tim Clark and/or Airbus that corroborates your answer, please provide it in your answer

Yes, and in the short-term they're also talking about re-engining the existing A380 with engines based on those on the A320neo as outlined here.

That link just says that they're considering an neo A380, not that the new engines would be based on the A320neo engines (CFM LEAPs.) It's extremely unlikely that they'd be using anything remotely like a LEAP on an A380 variant. Even with 4 of them rather than 2, it would be ridiculously underpowered. 4 similar engines (CFM56s) do power A340s, though.


text:
On a Gulfstream jet checklist, do you do the walkaround before or after disengaging the gust locks?
On a Gulfstream jet checklist, do you do the walkaround before or after disengaging the gust locks?
With small planes we generally remove the gust locks as we do the walk around, but with a larger jet I am wondering what the order of events is. Can you even see if the gust locks are engaged from the exterior of the aircraft or they purely internal and not visible?

May I suggest checking this item twice.  Relevant reading.

Since no one is touching this one, an (unqualified) effort may help others to respond.
There are several models of "Gulfstream" jet.  The Gulfstream IV has hydraulicly boosted control surfaces and an internal gust lock release lever in the cockpit.  The system is such that once the engines are started, hydraulic pressure prevents the lock from releasing.  The lock must be released first (check one).
The control surface actuators have a load limit warning light, and stop themselves from bending or tearing the gust lock if it is still applied.
A full control surface movement test - ailerons, rudder, elevator - before roll-out would detect if the gust lock was still engaged (check two).
The gust lock also prevents full application on the throttle (check three).
It would seem to be logical to OFF the gust lock near the top of the very first checklist, and check it again before rolling.


text:
Is a 61.31 solo endorsement a one-time thing, or does it need to be repeated?
The FAR 61.31(d)(2) reads that a person can act as pilot in command if they:

Have received training required by this part that is appropriate to
  the pilot certification level, aircraft category, class, and type
  rating (if a class or type rating is required) for the aircraft to be
  flown, and have received an endorsement for solo flight in that
  aircraft from an authorized instructor.

Is this endorsement a one-time thing, or does it need to be "renewed"? I met an glider instructor who claimed that my glider solo endorsement is no longer valid because my power license lapsed.

You didn't say which certificates and ratings you hold, but since you mention 61.31 I assume you're already a certificated pilot in a non-glider category/class (ASEL?) and you're receiving glider training.
The short answer is that a 61.31 solo endorsement expires only if the instructor added an expiration date as a limitation. Including an expiration date is optional, not required; see the Bennett interpretation:

The regulations of 14 C.F.R., however, do not prohibit an instructor
  from placing limitations, including an expiration date, in a §
  61.31(d) solo endorsement. See 14 CFR § 61.195(d) (prescribing flight instructor limitations on endorsements).

AC 61-65 is the reference for endorsements, and it has this language for a 61.31 solo endorsement (note the "optional" limitations section at the end):

A.71 To act as pilot in command of an aircraft in solo operations when the pilot does not hold an appropriate category/class rating: §
  61.31(d)(2).
I certify that [First name, MI, Last name] has received the training
  as required by § 61.31(d)(2) to serve as a pilot in command in a
  [specific category and class of aircraft]. I have determined that [he
  or she] is prepared to solo that [M/M] aircraft. Limitations:
  [optional].

Therefore, whether your 61.31 solo endorsement expires or not is determined by the wording of the endorsement itself. But as always, even if your endorsement is valid from the FAA's point of view, the glider school/club and their insurance company may have their own, additional requirements before letting you solo.
I don't understand the second part of your question: "my glider solo endorsement is no longer valid because my power license lapsed". FAA certificates never expire so I have no idea what you mean by "lapsed" (maybe this scenario?). In any case, I suspect that it might be better to ask that as another question; if you do, please tell us exactly which certificates and ratings you have.

Actually a solo endorsement for a student pilot is no longer valid for authorizing solo flights at or after 90 days of the endorsement.  A student pilot must obtain a new solo endorsement from a CFI thereafter in order to continue solo flights.  See 61.87 (n)

@CarloFelicione At least if I've understood it correctly, this question isn't about a student pilot. Tyler asked about 61.31, not 61.87.

Despite a low gross weight of only 5,520 lb the Eclipse 500 requires a type rating.
The OP should have warned this is not a "general" question, it is for special circumstances. FAR 61.31 would normally be for an already rated pilot that does not hold a endorsement for a "TYPE" certificate necessary for a special type of aircraft.
FAR 61.31 Is for approval to act as PIC of aircraft that require a "TYPE", rating commonly called "large", "turbojet", or "special" purpose aircraft (i.e. warbirds).
So, if a person already has a pilot's license, then FAR 61.31 is a lifetime endorsement.
A new FAR in 2017 (FAR 61.87(n)) places a 90day limit on student solos.
I doubt any instructors would approve a student pilot to fly solo in a aircraft that requires a TYPE rating such as the Eclipse 500. However, if the person were a student pilot, then the endorsement would be for only 90days per the limitation placed on student pilots in FAR 61.87(n).

Near as I know TBMs do not require type ratings although SOCATA does have a intital transition and recurrent training program for TBM pilots.

Your correct, I misread the lb for kg. I edited a better example - Thx.

Logbook endorsements for solo flight do expire - or no longer authorize solo flight - on after 90 days since the CFI endorsed tour logbook for solo flight.  See 61.87(n).  Also solo endorsements authorize solo flight only to the specific make and model of aircraft listed in the solo endorsement and cannot be applied to conduct solo flight by a student pilot other types of aircraft.

Since the question is about 61.31, I'm not sure why 61.87 is relevant?

But it is relevant to the OP’s question about whether an solo endorsement expires or not.

You're correct that a 61.87 solo endorsement expires but a 61.31 one doesn't unless the instructor added that limitation, as I explained in my answer. They're completely different endorsements (see the A.6, A.7 and A.71 examples in AC 61-65), so I'm still not sure why 61.87 is relevant in the specific case that Tyler is asking about.


text:
Is ADSB required in Class C airspace when the tower is closed?
Many Class C airspaces do not have a full-time tower and the airspace reverts to Class E or G when the tower is closed. The wording in CFR Part 91 § 91.225 doesn’t specifically say whether ADSB is required when the tower is closed and I can’t find any guidance from the FAA or AOPA on the matter.

(d)…no person may operate an aircraft in the following airspace unless
the aircraft has equipment installed that meets the requirements in
paragraph (b) of this section:
(1) Class B and Class C airspace areas
…
(3) Above the ceiling and
within the lateral boundaries of a Class B or Class C airspace area
designated for an airport upward to 10,000 feet MSL;

As when the tower is closed the airspace is E/G, then your question boils down to "is ADSB required in class E/G". Right? See also.

@mins Not exactly. The question boils down to whether the reversion to Class G or E also changes the requirement for ADSB or whether the Class C as depicted on the chart is in effect no matter what the status of the tower.

Are there any Class B or Class C airspaces that would be excluded by the phrase designated for an airport?  Why did they stick that in there?  Another ASE question in the making--

@quietflyer According to https://www.faa.gov/documentLibrary/media/Order/JO_Order_7400.11F_508.pdf there are no Class C currently that do not have an airport. I suppose it’s possible that when military facilities are shut down the Class C airspace could remain without a tower for a while.

If an airspace is only class C when the tower is in operation, then it is no longer class C airspace when the tower is closed.   In that case, the rules applicable to the class E or G airspace apply rather than class C, because the airspace is not class C at that time.

I would concur. The tower being open or closed has no bearing on the ADS-B requirement, except insofar as it affects what class of airspace is in effect.


text:
How do I find the magnetic bearing to the station in this question?
In my PPL trial test, I have the following question regarding an NDB:

Consult Figure 3, Illustration 6. On a magnetic heading of 160°, the
  magnetic bearing to the station is:

045°
205°
165°
270°

(See the attached figure, illustration 6)

Looking at the figure, I see a needle pointing to 045°. Therefore, I conclude that when my heading is magnetic north (as the heading of the aircraft is shown in the figure), the magnetic bearing to the station would be 045°. Consequently, I deduce that if I am heading 160° magnetic, then the bearing to the station would be 115° to my left, i.e. 360° - (160° - 45°) = 245°.
The reason I think this is because, as I am turning eastwards the magnetic bearing to the station will decrease until I reach a heading of 45° magnetic at which point the magnetic bearing to the station would be 0°. As I turn eastwards more, the magnetic bearing to the station would flip around at 360° and keep decreasing. I need to make a starboard turn 160° - 45° = 115° more to reach the desired heading 160°, so by that time the bearing would decrease from 360° by 115° to reach 360° - 115° = 245°.
Nevertheless, the test claims that the correct answer is 205° (which I'm guessing is, for some reason, calculated as 160° + 45°). Could you kindly explain what is wrong in my thought process or interpreting the ADF instrument?

Based on the correct answer below, it is now clear to me that the instrument depicted is an ADF, not a VOR, as it depicts the relative beating TO the station, but with a Fixed Compass Card (see http://www.navfltsm.addr.com/ndb-nav-adf-1.htm). The magnetic bearing to/from the station does not change with heading.

I edited your question to fix some terminology: the pictures are of an ADF, not a VOR receiver. A VOR would have a to/from flag.

I think the figure is just intended to illustrate the bearing to the NDB relative to the aircraft, and not the magnetic heading of the airplane. So when they give you your magnetic heading of 160, you're still using the bearing of 045 relative to your aircraft, which gives 205 magnetic.

MB=RB+MH
for fixed card ADF. as shown here
Airplane now heading 160 from north " nose of airplane "
relative heading now is 45 from heading of airplane " from nose " it means station is located 45 degrees from your heading which is 160 degrees north
so the magnetic bearing to the station equals 160+45=205
hope it helps


text:
Why do military turbofan engines use a low bypass ratio?
I know that the most civilian engines use a high bypass ratio which is good for fuel economy and noise reduction.
What prevents military engines from using the same technology instead of opting for low bypass engines?

Because the priorities for military aircraft (engines) are different. While it is true that the high bypass turbofans have better fuel economy (in cruise) and are less noisy, the low bypass engines offer significant advantages when we take into account their intended use in combat aircraft, such as:

The response of the low bypass turbofans to throttle adjustments is faster compared to the high bypass turbofans; the inertia is less and less air mass is involved (for increasing the velocity)- This is important during combat, when thrust requirements change rapidly.
They have less frontal area, reducing the drag produced. For aircraft expected to fly at supersonic speeds, however briefly, this is important.
Better thrust to weight ratio- 6:1 in Trent 1000 Vs 9:1 F119 (used in F-22 Raptor)- Even if the actual thrust produced by the low bypass turbofans is lesser, they produce more thrust per kg of engine, which means that the engine can be more compact in size.
The low bypass turbofans are more efficient at higher speeds compared to the high bypass turbofans.
The lesser size of the low-bypass turbofans mean that the aircraft can be made stealthier by 'burying' the engines in the fuselage, which is all but impossible in case of high bypass turbofans.

I can see you often referring to the size advantage of the LBE , so meaning if you have the same size(physical dimensions) of both engines the LBE will have higher thrust than a HBE?

Yes, a higher bypass ratio means slower airflow which is good for efficiency at lower speeds, but means you need a larger overall diameter for a given thrust.

It's not military vs civilian, but subsonic vs supersonic-capable
Note that subsonic military aircraft use the same engines as civilian aircraft, even if their names might be different.

The KC-135 used initially the J-57 which was called JT-3C when used in the Boeing 707-120. Now they fly the CFM-56, which is used on the Boeing 737 and the A320.
The C-5 Galaxy uses the GE TF39 which became the CF6 when mounted to a Boeing 747-100 or a DC-10.
The Fairchild A-10 uses the GE TF34 which is called CF34 when mounted to civilian aircraft like the Bombardier Challenger.

No, the differences arise only when the aircraft is designed to fly supersonic. This requires a very different approach to the integration of the engine:

Supersonic aircraft engines are mounted close to the centerline. If possible, they are straight behind the intakes, so the intake flow does not need to change direction. Exceptions like the SR-71 are rare.
Supersonic intakes are longer and have sharp edges as opposed to the short, blunt intakes of subsonic aircraft. Also, most have a variable geometry to adapt to the very different flow conditions at supersonic speed.
Since it is the job of an intake to slow down the air going into the engine, supersonic intakes cannot have a big capture area, or their spill drag in supersonic flight would be excessive. Supersonic engines need to create their thrust with much less airmass than purely subsonic engines. Forget stealth, this is the real reason for the smaller diameters of supersonic-capable engines.
The nozzle of a supersonic aircraft is also variable, in contrast to the fixed nozzle of subsonic aircraft. This again helps to adjust it to the flow conditions, but in this case the major difference is between reheat on and off. Afterburning engines are capable of much higher exit speeds to compensate for their smaller diameter. They accelerate less air to a higher speed to create comparable thrust.
The last point mentioned it, but it deserves a bullet of its own: Supersonic engines use afterburners in order to have enough thrust for going supersonic at all. The hot exhaust gasses have a much bigger volume than the cold intake flow which needs to be accommodated by widening the nozzle.

Note that the civilian Concorde used also a variable intake and nozzle and afterburners. It had an engine which was used on the BAC TSR-2 before, a supersonic military aircraft.
The real distinction is not between civilian and military, but between purely subsonic and supersonic-capable. Initially, both was achieved with the same engines. The J-57 mentioned above was also used on the supersonic F-100 military jet. Only in the 1960s did those lines diverge, and the subsonic aircraft grew ever bigger low-pressure compressor stages. These were again driven by the high-pressure cores which were used on supersonic aircraft.
Background
Thrust is air mass flow multiplied by the speed difference between flight and nozzle speed of the engine. To increase thrust, subsonic engines try to maximize mass flow (by increasing the bypass ratio) while supersonic engines rely more on increasing the nozzle speed (by using afterburners). Since net thrust is only possible when exit speeds are higher than the flight speed, the engine's exit speed needs to increase with the design flight speed.
The core engines do not differ much - after all, the intake will make sure that air reaches the engine at a speed of Mach 0.4 to 0.5, regardless of flight speed. The core of the General Electric F110 (installed in the F-15 and F-16 fighters, among others) became the core of the CFM-56 turbofan which is used in the Boeing 737 or the Airbus A320. The main difference is in their bypass ratio. The slower the design speed, the bigger the bypass ratio may become. At very low speed, the ungeared, shrouded fan is exchanged for a geared, free spinning propeller, in other words, the jet changes to a turboprop. The intake and nozzle, however, are very different indeed.
The optimum bypass ratio changes continuously, but since the drag coefficient drops after crossing Mach 1, airplanes are either designed for a maximum Mach number of 0.9 or less, or 1.6 and above. The corresponding bypass ratios today are up to 12 for subsonic engines, and less than 1 for supersonic engines. This produces a sharp boundary at the speed of sound, and many military engines designed for supersonic flight lost their afterburners and were fitted with a big fan to become the engines for subsonic transport aircraft.
The differences between sub- and supersonic engines grow bigger the more you move away from their core. High-pressure compressor, combustion chamber and high pressure turbine look and work the same, but the low pressure compressor of subsonic engines swallows a lot more air and has a much bigger diameter. Supersonic engines in turn mostly have an afterburner. The biggest difference, however, are the intakes (large pitot intake with blunt lips for subsonic aircraft versus adjustable spike or ramp intakes for supersonic flight) and the nozzle (fixed for subsonic flight versus a complex, adjustable convergent-divergent nozzle for supersonic flight). This is due to the very different air speeds and the much higher exit velocities required for supersonic flight.

Look at the intake section of the XB-70 pictured above (source). The capture area is rather small, and then the intake tube widens to enable the slowing of the airflow. The inclined sidewalls of the intake section cause a lot of drag at Mach 3. Now think the six GE YJ-93s are replaced by engines with an even bigger diameter. The increase in wave drag due to the even blunter intake would cancel out all advantages of a higher bypass ratio.
What is less obvious is the fact that this intake section also creates maybe half of the overall thrust of the propulsion system. But this answer is already too long, so I save this for another answer.

How do engines capable of going supersonic without using afterburners (eg on the F-22/35's) fit into this discussion?

this intake section also creates maybe half of the overall thrust of the propulsion system - is that for sub or supersonic engines? I'll go ask the question

@DanNeely: All supersonic engines need high exit velocities, and the afterburner helps, but is not essential. If the engine is big enough, the afterburner is not needed. Note, however, that the same thrust would need a smaller afterburning engine, because it can create the same thrust by accelerating a smaller air mass to a higher exit speed.

@FreeMan: This is only true at high supersonic speed. Simply put, the high intake pressure due to pressure recovery inside the intake pushes the aircraft forward.


text:
Are sun's UV rays more harmful on an airplane at high altitude?
Most airplanes fly at >30k feet, way into the stratosphere / mesosphere where sun's UV rays aren't filtered by lower atmosphere layers.
If the windows of the plane are open and the sun is shinning right on a passenger, will the UV rays be more harmful than those on the earth's surface?
Are there any long term effects if a passenger is exposed frequently?

Sounds like a good way to get a tan!

30k feet is not necessarily way into stratosphere. Aircraft usually try to fly in the tropopause where it is coldest and thus engines have highest thermodynamic efficiency (which means lowest fuel consumption). Tropopause ranges from 30kft (when it is cold like on poles) to around 56kft (when it is hot like on the equator), the later being well above what transport planes can do.

When you write "open" - you mean "unshuttered" - right?

@RedGrittyBrick It gets stuffy in there. Sometimes it's nice to have a little fresh air.

You are much closer to the sun, so yes you would get quite a burn. Though its the perfect time to bring your solar charger. It would charge a lot faster ;)

Most commercial aircraft fly that high.  There's a lot of GA aircraft out there that are not affected by this.

@Ethan: Icarus flew too high, and the wax keeping his wings together melted. However, today we know earth is 5,000,000km closer to the sun in January than in July. So, altitude of an aircraft doesn't count here ;-)

@Ethan Don't forget that the sun's electricity get's stronger as you climb higher, too.

Hmmm, opening the window at 30.000ft, where the air temperature is about -40°C/-40°F, air speed is extreme, you can't survive without oxygen, and you want to put your arm outside???
Well, if you really do, you'll get a sunburn quite fast. I got a sun burn within an hour in an altitude of 3500m / 12000ft, though I was tanned due to two weeks at the beach.
The ozone did already absorb a large fraction of the UV-C radiation, but as most of the air mass is already below you, the rest of the sun light will not have been filtered so much.
So, let's close the window.
To my knowledge, side windows and canopies are made of some kind of polycarbonate like or Plexiglass.
CERN measured the transmission of light through a 2mm sheet of plexigas and came to the result that no light below ~350nm, passes this sheet. Depending on source, the UV region starts below 380-400nm.

Source: https://cds.cern.ch
Keep in mind that the windows are usually thicker, which makes this step in the diagram much steeper.
So, there isn't much UV left which can cause a sun burn, but let's take the data from rredc.nrel.gov to calculate how much light you get and compare it to the light at ground. I found a function describing the data from CERN quite well, and applied it to the sun spectrum data (without atmosphere) twice, to get a Plexiglass window of 4mm thickness. So, this is the worst-case, with no air above the aircraft pre-filtering the sunlight.
Here is the result, which shows that sunlight is much more intense, and its color is heavily shifted to blue. But the intensity drops to zero, just where the UV-A range starts. Even, if you put the beginning of the UV-A range to 400nm, the intensity is still lower than at the ground.

Wind shields of larger aircraft are usually a quite thick composite material of glass and some plastics, which should absorb UV the same way as polycarbonate does, if not better.
So, I don't see any evidence that you get more UV light in an aircraft than on ground.
However, you should not underestimate cosmic radiation, which is absorbed by our atmosphere quite well on the ground, but not at high altitude. A transatlantic flight is equal to an X-ray photography of your chest. Flying staff is an occupation group exposed to much higher radiation doses than any other group and it's dose usually is supervised.

EDIT:
As @PeterKämpf pointed out, Plexiglass is only one material used, and it is not a polycarbonate, which I didn't notice. But polycarbonates don't differ much concerning UV transmission, as the following diagram shows. However, I also read that polycarbonates - in contrast to plexiglass - are not UV hard and need an UV blocking coating when used outside.

Source: www.plasticgenius.com

"A transatlantic flight is equal to an X-ray photography of your chest." Huh, didn't know that! If I ever start commuting across the Atlantic I'll start paying attention to this.

Set a large sheet of x-ray film against your seat before you sit down and get a free chest x-ray thrown in for the price of your flight!  :)

@FreeMan: Unfortunately, that's not how it works. Cosmic radiation is not X-rays, it rather consists of electrons, positrons, pions, muons, gamma rays and other strange stuff. It's just that this does about the same ionization to your body as X-rays. And in contrast to X-rays, they don't care much about bones and tissues, so the x-ray film would show a quite blurry picture.

Color me disappointed, @sweber. I was just about to tell the wife we needed to take a medically necessary flight somewhere fun.  ;)

nice answer.. btw by opening the window I meant the shutter is open.. not the physical window.. :)

I'm having some trouble with this answer.  Doesn't it seem to imply that I don't have to worry about sunburn / UV/ skin cancer when flying a sailplane, since the canopy is several millimeters thick?  That doesn't seem to mesh with my own experiences or with the understanding of the soaring community.

You're right. According to the WHO1 at 30,000+ feet, UV rays are more intense. They're around 90% more intense, which is enough to cause some pretty nasty skin, and eye damage.
Pilot's do have a higher risk of skin cancer2. Although, the jury is out on why this is the case. Most cockpits themselves are made of a different set of materials.
The FAA itself does not have any requirement3 specifically on the opacity to UV rays for windows. Though, they point out that typically passenger cabin windows have a protective layer, and typically use some acrylic or polycarbonate. The regulations themselves state the the material must be tolerant to UV exposure itself. Polycarbonate4 absorbs most of the UV spectrum. Acrylic on the other hand absorbs UVB, and UVC, the most harmful type of UV radiation5. It, unfortunately, allows some component of the UVA portion of the through (less than 50%6). On top of this, most airlines glaze their windows, blocking even more light.
Some modern aircraft utilize electronics in the windows to dim them. The materials that are involved in this allow for better filtering of light, and in addition, allow for the cabin crew to dim the entire cabin in high light situations7.
In conclusion, you're a pilot, there may be some higher risk in exposure to UV rays, and you should take appropriate precautions, such as wearing sunscreen. If you're a passenger that flies often, it's probably okay, and no worse than taking a walk in the sun, but if you have very sensitive skin, wearing sunscreen will be an effective way to prevent the little damage that can occur. Fortunately, airplanes are getting more advanced every day, and the risks are becoming fewer, and fewer.
Sources

http://www.who.int/uv/faq/whatisuv/en/index3.html
http://www.nytimes.com/2012/08/12/travel/faq-frequent-airline-questions.html
http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC25-775-1.pdf
https://en.wikipedia.org/wiki/Polycarbonate
https://en.wikipedia.org/wiki/Ultraviolet
http://www.eplastics.com/Plexiglass_Acrylic_Sheet_UV_Filter
http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_06/AERO_Q406_article4.pdf

Why doesn't FAA have any requirement if UV rays are 90% more intense at 30k feet

They have requirements around UV-resistance, but not passenger safety in terms of UV exposure. My guess is that most airplanes are already good enough in this space, and it really doesn't need regulation.

UV protection for the general public and for workers (i.e. cabin crew) is not specific to aviation. There is an EU regulation covering the maximum UV levels from sunbeds used for artificial tanning, for example.

As per Wikipedia, the ozone layer is from approximately 20 to 30 kilometres (12 to 19 mi) above Earth. 30,000 feet is 9.1 km which is below the ozone layer, hence the UV rays passing below this range would have been filtered already.
There are some side effects on skin (cancer) and eye - refer for more details. If this is causing severe problems, then FAA/FAR would have had the regulations to fly below a certain altitude. I don't think there will be any severe effects on the skin as well on the eyes from the UV rays below the ozone layer.
Also per FAA Safety, all civil aircraft cannot cross Class A (flying under IFR) airspace cannot exceed FL 600 (~60k ft) which is almost below the ozone layer, so no to the question of exposing to direct UV under these altitudes.

UV exposure supposedly increases aout 4% every 1,000 feet so folks living in Colorado would get about 25% more UV than people living at sea level.  However, some of these comments appear to say all UV exposures below the ozone layer (60,000 feet to 100,000) are equal. Hmm...  I have always heard that airline personnel have a high risk because of spending so much time at 30,000 feet plus.  I don't have a technical background but I do know that ozone blocks UVB more than UVA and the air itself may absorb some as well.

There's indeed more UV at cruise altitude, but the metal and the windows of the aircraft block it completely. The higher risk you mention is due to cosmic radiation. This is much higher at altitude, and can not be shielded by the windows nor by the  aluminum body.

The water in the air can block a lot of UV.

The material of the windows will filter most or all of the UV radiation from the incoming light. That's the reason as well why you don't get a tan driving your car with the windows rolled up (yes, car windows are made of different materials, but the effect is the same).

Yes, the level of UV radiation at high altitude is more intense than at low altitude, which is why wearing eye protection and protecting the skin against exposure at high altitude is important.
But unless you were to fly at 30.000 feet in an open aircraft without windows there's no reason to worry about that when flying. And if your window were to blow out at that altitude you have more serious problems than getting a bit of a sunburn :)

I'm having some trouble with this answer.  Doesn't it seem to imply that I don't have to worry about sunburn / UV/ skin cancer when flying a sailplane, since the canopy is several millimeters thick?  That doesn't seem to mesh with my own experiences or with the understanding of the soaring community.  Also-- there are studies out saying that people who drive a lot, are more prone to cancer on the right-hand sides of their faces, since that is the only side that is likely to be in direct sunlight while driving.


text:
What are these suffixes used after the call sign?
I often play a flight simulator game Infinite Flight (http://www.infinite-flight.com) on my iPhone. The game lets you choose the following suffixes with your call sign.

Heavy
Super
Flight of 2
Flight of 4
Flight of 5
Flight of 6
Flight of 7
Flight of 8
Flight of 9
Flight of 10

I am aware what "Heavy" means but now aware about the rest. Can someone let me know?
Thanks

you may rather like to ask this question here


text:
How is the amount of time for an A check or daily maintenance determined?
How can the time for daily maintenance or A Check be calculated for different aircraft types?

Is there any exact formulation depending on the aircraft specifications?
 P.S.,I'm very new to the aviation field.

The time taken for the daily maintenance or 'A' checks (or any other checks for that matter) depends on a number of parameters like:

The aircraft configuration.
The experience and skill level of the aircrew.
The condition (or age) of the aircraft and its components.
Requirement of any special checks (whether manufacturer/regulator mandated or operator requirement)

Usually, the checks to be carried out during each schedule (hourly or calender based) are determined by the manufacturer (sometimes in co-ordination with the operator) and laid down. The time required is then calculated by actually timing the operations and adding correction factors or by statistical analysis over a period of time.
One thing to note is that this is not exact and will vary based on a number of factors. For the same checks, different operators (and manufacturer) may allot different time periods. If two different checks (for e.g. airframe and the engine) are required to be carried out at the same time, the time required will differ.

This answer is not specific for A-checks, but covers the whole maintenance effort.
Try Eddins-Earles, Mary: Factors, Formulas and Structures for Life Cycle Costing, Eddins-Earles, 89 Lee Drive, Concord MA 01742, USA, 1981
It's a bit dated, but has a wealth of data.
Another source would be Fabrycky, Wolter J.; Blanchard, Benjamin S.: Life-Cycle Cost and Economic Analysis, Prentice-Hall International. ISBN 0135383234.
Also, the white volume (I think it is No 8) of Jan Roskam's collection is a good start. Roskam, Dr. Jan: Airplane Design, Roskam Aviation and Engineering Corporation, Ottawa, Kansas 66067, USA, 1990.
Generally, this is not exact science, so exact times cannot be expected. With experience, each operator will be able to estimate how long things take, but you do these checks to find possible damage which needs to be taken care of. A lot depends on the training and experience of the maintenance crew. The best way to approach this is with statistics.

To answer your first question:
The manufacturer (OEM) usually publishes an estimate of maintenance man-hours (MH) needed for each task within their Maintenance Planning Document (MPD). For non-MPD tasks, source documents such as Service Bulletins usually also have an estimate.
When an A- or C-Check work package is created, the OEM's estimates for each task can simply be added up to get a rough idea of the total number of MH needed. HOWEVER: this is just an estimate! The OEM's figures assume that the work is being carried out in ideal conditions, i.e. the tools are all at hand; paperwork is printed out; access to the aircraft is readily available; and the mechanic is well versed in doing that task. The OEM's estimate therefore needs to be adjusted. I've seen various organizations use factors varying between 2 to 4 i.e. if the OEM says one hour, you plan for between two to four hours. The factor will typically vary depending on factors such as:
- facilities / equipment available at the maintenance location;
- experience and skill levels of the technicians;
- age and condition of the aircraft;
- and even the type of check (e.g. A-Check vs C-Check).
Once the total MH for the A- or C-Check package is calculated, you can get a rough estimate of the ground-time you'll need for the check, based on the manpower you have available.
HOWEVER, a word of caution! As Peter says, this is not an exact science! Remember that the number of MH is different from the actual time it takes to do the task (known as "elapsed time")... E.g. time for a sealant to cure doesn't count towards the MH, but does still need time in the real world. Remember, just because a woman can deliver a baby in nine months, doesn't mean nine women can deliver a baby in one month!
Ideally, the company should have a process in place to gather and analyze data on planned MH vs utilized MH and planned vs utilized ground-time and incorporate this into their production planning activities.
To answer your second question:
As can be seen above, there is no "exact formulation". The calculations based on the OEM's MPD and source documents provide a ballpark figure, to which you then need to apply your engineering judgement and experience. This is where data gathering and analyses can be invaluable to an organization's planning process.


text:
What is the difference between fixes and waypoints on an arrival plate?
This is a followup to my other question on this topic. Figured I'd just make it a whole separate question.
The plates below show STAR arrivals to KMEM. The points along the route are marked with two different symbols. When I look in the FAA guide it refers to the triangular symbols as non-reporting fixes and the star shaped symbols as non-reporting waypoints. What is the difference between the two? Why are they marked with different symbols?

The triangle points can be determined from conventional navigation (radial/dme and/or radial/radial). The 4-point star waypoints are only defined as RNAV waypoints.

As described in the answer to the previous question, all of the points on the chart are both waypoints and fixes. The difference between the printed icons is how they are identified from the air.
The waypoints marked by hexagons, some with darkened edges and some printed inside a square, note where the waypoint is on top of a VOR. This includes Razorback, Walnut Ridge, Gilmore, and Memphis. The icons with bolded sides are a VOR collocated with TACAN; inscribed inside a square notes a VOR collocated with a DME station.
Triangles are waypoints determined by a radial and distance from a VOR station. The star icons are determined by an RNAV (area navigation) system, which does not require the aircraft to fly a particular VOR radial to determine its course. Note that the procedure you provided is not available for RNAV-capable aircraft, likely because there is an RNAV arrival procedure that is preferred by ATC.

To fly the procedure, starting from the left, a pilot would identify the Razorback (RZC) point by their CDI showing that they had flown over the beacon itself. The next waypoint is MARBI; that is determined by flying along the 098 degree radial to a distance of 34 NM from RZC. Similarly, IGLOO can be identified by flying the 098 degree radial another 85 NM for a total distance of 119 NM. The distinct icons tell pilots how to identify the waypoints using their onboard equipment, but they otherwise have the same meaning.

Thank you. You just cleared it all up for me. I realized I uploaded the wrong plate. This one doesn't have the star-shaped waypoints. I went to find the one I intended and now I see that the star shaped icons are only on the RNAV plates since they don't coincide with a radial from another VOR. So they can't be used without RNAV. +1

According to the Pilot/Controller Glossary:

WAYPOINT− A predetermined geographical position used for
  route/instrument approach definition, progress reports, published VFR
  routes, visual reporting points or points for transitioning and/or
  circumnavigating controlled and/or special use airspace, that is
  defined relative to a VORTAC station or in terms of latitude/longitude
  coordinates.

and

FIX− A geographical position determined by visual reference to the
  surface, by reference to one or more radio NAVAIDs, by celestial
  plotting, or by another navigational device.

They are pretty much used interchangibly, but a fix is just a point in space, where as a waypoint is a fix where the pilot might actually do something, although this doesn't always hold (e.g., the MAP)
Sometimes one or the other may be built directly into the nomenclature, like

DME Fix
Final Apprach Fix (FAF)
Visual Descent Point (VDP)
Missed Approach Point (MAP)

Sometimes you have to be very careful using fix or waypoint:

Missed Approach Point (MAP) -- where the land/missed decision must be made. It uses point and not fix because it may be determined by DH, a timer, or a GPS fix, even on the same approach chart.
Missed Approach Fix (MAF) -- where the missed approach hold is

In this example for the ILS at KMEM, the MAP may be determined either by:

466MSL DA with a working GS
4:18 seconds @60KIAS from the FAF with GS INOP


text:
Washout filter for pitch and roll damper
Washout filters are generally described in context of yaw channel where they  allow the turn command signal to not be dampened by the yaw damper in the feedback circuit as the low frequency signal is the pilot command.
By the same reasoning, are washout filters not necessary in pitch and roll channels also where damper may fight with the pilot  commands?

Dampers are commonly implemented for pitch, roll and yaw damping. However of these three, only the yaw-damper has to allow a non-zero static component:
During a turn with constant bank angle, the pilot has to command a steady rudder input in order to achieve a coordinated turn. This results in a constant non-zero yaw-rate which a yaw damper without washout filter would continously counter-act. In pilots-terms, the yaw-damper would continously fight the pilots rudder command by counter-acting it.
For this reason a washout-filter (or high-pass filter) is introduced: This filter will only let through the high-pass component of the yaw-rate, therefore filtering out the steady-state yaw rate the pilot commanded. The yaw damper therefore does not "see" this steady state yaw-rate anymore and therefore does not fight it anymore.
For reference, I find it pretty nicely explained in this open access lecture.

Shared document (https://mitindia.edu/images/pdf/avionics_ppt/pitchrolland%20yawdamper.pdf) is very useful. As per page 12 of doc, washout is also required in pitch channel during pitch axis maneuvering.

Great! If you like my answer, please upvote it.


text:
Doubt in the Coriolis component of the net force acting on the aircraft
I dig a little and got to know that the force equation in 6DOF are nothing but a mathematical depiction of the fact that for a translating & Rotating body in 3D,The net force is the Translational force +Coriolis force.
In all the text books Coriolis force is defined as
$-2m(\boldsymbol{\omega} \times \textbf{v} )$.
Where  $\times$ = Vector product, $\boldsymbol{\omega} $=Angular velocity, $\textbf{v}$=Linear velocity
So if I follow this, Coriolis force in x direction should come as $-2m(qw-rv)$.
But in the Fx equation of the 6DOF,the Coriolis term is coming as $m(qw-rv)$, there is $-2$ missing, and off course that is also correct but it's confusing.
Can anyone help me in filling the dots that I'm missing?

I think this question is better suited on https://physics.stackexchange.com/

According to How Airplanes correct for the Coriolis Effect, Coriolis force requires a correction of 0.00021 % of the thrust. But the explanation seems great.


text:
What is the current state of the practice regarding surveillance and surveillance data integrity?
I am experiencing difficulties in finding out exactly how air traffic surveillance works in practice, and more specifically what is done to verify the integrity of surveillance data.
ADS-B and other "modern" surveillance protocols (i.e., protocols relying on data package exchanges, squitters or interrogations) are  mostly transmitted in clear-text. The cybersecurity community has been claiming for a decade that there is a high risk of bad data injection which could be catastrophic. Security experts imply that ATC experts are too focused on safety, that they lack a cybsersecurity mindset, etc. The ATC community, on the other hand, has claimed that security experts don't understand the domain well enough to be able to gauge risks, saying that multilateration is always there to evaluate the integrity of ADS-B messages in case of doubt, saying that surveillance is not only these protocols but also voice communication, acars, etc. What I want is not offend either party and get a view as holistic as possible.
Most of what I have found is from EUROCONTROL, deliberables from projects 15.04.05a and 15.04.05b. Typically, this is what it says:

Ground stations capture ADS-B traffic, potentially verify the data using WAM reports, potentially verify the data using other GS reports (not shown on the figure but I think I read it somewhere), then send the data to an SDPD, which can also use WAM reports as well as radar data to check the data. There can be multiple SDPDs exchanging data for even more verification and data fusion. Meanwhile, there are multiple data integrity check, such as angle of arrival measurement, power measurement vs range correlation, etc..
Then, I read that there is also multilateration possible using ADS-B squitters and TDOA with the so called Mode-S BEAST protocol format that provide nanoseconds precision for the timestamps instead of the initial millisecond.
So, what is the real, current state of the practice? Is the EUROCONTROL schema I mentioned above is the norm now and fully deployed, or not at all? What did I miss? Thank you very much.

If by "BEAST protocol" you're referring to the "Mode-S Beast" data format (http://wiki.modesbeast.com/Mode-S_Beast:Data_Output_Formats) then be aware that's just a format that is used by amateur observers (and possibly unofficial, commercial tracker networks like flightaware, etc.).

Yes you're absolutely right, I meant to say format, not protocol.
Are you sure it is only used by amateur observers? I have heard there are (well-known) ATC systems manufacturers working on MLAT solutions (at least WAM) based on the Mode-S BEAST format.


text:
Why is this unit attached to the main landing gear not a common unit for towing or pushback?
Less loading is applied to the fuselage with this method compared to towing or the towbarless way. Why is it not really common?

I'd like to detail this. There's my point, wouldn't it reduce cycles of loading to the fuselage, less fatigue resulted. Then we can eliminate shear pin & speed limit such stuff, doesn't it ?
In my opinion. For safety. This is much safe then the towing method.

Wouldn't this need to apply a lot more force since the mains are much closer to the CG/CM than the nose wheel?

No, it's same of moving a object forward. (except turning)

Then what about turning? turning plays a huge part in towing aircraft in and out of gates

What if we bring another car to shear the Nose. They operated together. isn't it better than towing.

You've got a plane that has X take off mass, and Y rolling resistance in the gear. No matter where the force is applied, it takes the same amount to get it moving...

I knew it. There's my point, wouldn't it reduce cycles of loading to the fuselage, less fatigue resulted. Then we can eliminate shear pin & speed limit such stuff, doesn't it ?

I think it might not have enough clearance for smaller aircraft, while a towbar would work with pretty much everything.
Also the force you apply needs to be pretty much the same, independent from where you push/pull, as you only need to overcome the rolling resistance of the landing gears. The airframe and landing gears are sized for much larger loads, so there is not a lot of saving in my opinion.

I think the chearance issue can be solve by another design.

The clearance on a 737 is only a few feet (see this video for a sense of scale). Yes, it might be conceivable that someone could design a tug that fits in there (maybe, tugs need a significant amount of mass to have traction, they can't just be arbitrarily small), but the driver wouldn't even be able to sit upright. And the clearance issue is even worse on a regional jet.

Yes, it is. actually those bottom antennas & valves are big problem.

Ultimately you would need two per aircraft to have any meaningful stearing. Towing is generally used to push back from the gate, a time when a tight turn is generally needed so taking advantage of the pivoting nosewheel is a big consideration.
Most aircraft tricycl gear from a Cessna 152 up though an A380 are towed from the nose wheel so designers are well aware of this when laying out nose gear specs.

Yeah, it does a big advantage. but this is insane of pulling the whole fuselage periodically. Then, manufacturer told you to buy a fuse pin for this and you have to follow it. We had to deal with such stuff. well, incident happen every year.

@user35367, the fuselage has to withstand much greater loads (from pressurisation and aerodynamic forces), so towing is not a critical factor. The greatest stress is local to the nose gear mount when, indeed, towing starts without brake release.

@Zeus Previous incidents not only result from towing without brake release. They were caused by maybe a sharp turn, an invisble slope or drifting on wet surface etc. But yes, nose gear withstand the greatest stress. Hence, we have to use fuse pin. somehow it always break. can we stop use them? yeah, I wonder if we might start to use PPU (push unit).


text:
Which wing stalls first in a level coordinated turn?
I was told that in a level coordinated turn the inside wing stalls first because it has a higher angle of attack (AoA).
Now, I have always thought that in a level coordinated turn, the wings must have the same AoA and so if stalled the nose will just drop.
I know the differences in AoA in climbing and descending turns and which wing stalls first. I also know that in a level turn the outer wing must travels faster and so will generate more lift.
Is it because since the outer wing has more lift one would need to stop the overbanking tendency by holding 'counter aileron' input, (roll right to hold a left turn), so the inside wing now has a higher AoA overall?
Edit: after some more thoughts on this, I think I have figured it out! Since the outer wing produces more lift due to travelling faster, the inner wing will need to have a higher AoA in order for lift to be the same from both wings (hence the counter aileron inputs). Is this correct?

Comments are not for extended discussion; this conversation has been moved to chat.

...the outer wing produces more lift because it is traveling faster

Let's take a 2000 lb plane in a level 45 degree turn at 100 knots.  Radius of turn is:
 R = V$^2$/(11.26×Tan bank angle) = around 900 feet
My aircraft has a 55 foot wingspan.  Draw it to scale, or calculate the Radius of the outer and inner wing tips in that circle:
Since the bank is 45 degrees, the horizontal distance between wing tips is 0.707 × 55 feet = around 40 feet
 Turn Radius inner wingtip:  880 feet
 Turn Radius outer wingtip:  920 feet
Wingtip velocities:
 Inner:  100 knots × 880/900 feet = 97.8 knots
 Outer:  100 knots × 920/900 feet = 102.2 knots

How does one design an aircraft not to roll uncontrollably into a turn?

First, we can calculate the roll torque created by the lift differential of the inside and outside wings:
Vertical lift required:  2000 lb
Total lift at 45 degrees:  2000/.707 = 2800 lb
Difference in lift (excluding fuselage and wingtip effects):
Average speed of inside wing (tip to fuse): 99 knots
Average speed outside wing: 101 knots.

Lift is proportional to V$^2$

99 knots$^2$ = 9800
101 knots$^2$ = 10200
Lift outside wing = 10200/20000 × 2800 = 1428 lbs
Lift inside wing = 9800/20000 × 2800 = 1372 lbs
Lift differential = 1428 - 1372 = 56 lbs
Roll torque = 56 × 55/4 (wing midpoint to CG) = 770 foot/pounds
The one obvious asymmetrical part of the aircraft is the vertical stabilizer.  Combined with the rudder, it forms an airfoil which imparts roll torque on the aircraft.  In a properly coordinated turn, rudder into the turn should be providing sufficient roll torque away from the turn to counter-act differences in lift.
Let's plug in some numbers to see if this is possible:
Vertical fin/rudder height: 6 feet
 midpoint = 3 feet
 "lift" required by Vertical airfoil: 770 foot/pounds ÷ 3 feet = 256 lbs

Lift is proportional to Area

Even with the same coefficient of lift, wing lift roll torque differential can be balanced with a vertical surface less than 10% of the total wing area!
This is in addition to the rudder's primary job of countering adverse yaw created not only by the ailerons, but also by the velocity differential of the wings.  Alas, more lift = more drag.
As mentioned by Peter Kampf, a turning aircraft will also try to "flatten", or roll away from a turn due to "centrifugal" forces.

What if my plane has an overbanking tendency?

Seek out expert advice specific for that type of aircraft.  It may come down to a choice of evils.  Aileron away from a turn, in addition to increasing the AoA of the inside wing, also creates proverse yaw.  Now you have to reduce rudder or the plane will skid.
Another option, particularly with aircraft that have very large wings and small tails, is to nudge to nose to the outside enough to use the dihedral effect of the entire aircraft to control the roll.  But these are both compromises to a properly coordinated turn.
The greatest evil of all is to turn at a dangerously low airspeed.  This is where all the other sins rear their ugly heads, and is why any flight technique other than coordinated should be tried first at least "2 mistakes high".
Finally, we all must consider one non-aerodynamic factor which may influence aileron and rudder input in a turn: forces created by the engine and prop.  It is entirely possible that additional inputs must be made to control these forces, even if the aircraft is aerodynamicly coordinated.  Strong evidence of this is the fact that power must be increased to hold level flight in a turn.
The proof for best control inputs for the lowest drag in a turn is to see if the aircraft climbs, holds, or loses altitude for each setting tried at a constant power setting.

Gliders are those big span, small tail configurations and they circle at very low speed a lot. Indeed, one of the useful techniques is to point the nose a bit away from the center of the turn in order to let dihedral do its magic.

Since the outer wing produces more lift due to travelling faster, the inner wing will need to have a higher AoA in order for lift to be the same from both wings (hence the counter aileron inputs). Is this correct?

Yes, it is. Technically, the AoA is the same left and right in coordinated flight, but the aileron input reduces the stall margin on the side of the down aileron. But not every airplane needs to add aileron input in a steady turn. For some, the uprighting inertial moment is enough.
Where you DO find a difference in AoA over span is in a climbing or descending turn.
To answer your question: In almost all cases it is the inner wing which stalls first. The lower speed and Reynolds number already lower the stall margin a bit and some trailing-edge-down aileron deflection to compensate for the lower lift from lower dynamic pressure there will make sure that this wing will stall first.

Re -- "Technically, the AoA is the same left and right in coordinated flight" -- is there an accepted standard for measuring AoA (of portion of wing with ailerons) when aileron is deflected?

@quietflyer - Technically it should be measured from the instantaneous zero-lift line.

@quietflyer AoA is defined as the angle between the airfoil's chord at zero deflection and air, regardless of actual deflection.

"I was told that in a level coordinated turn the inside wing stalls first because it has a higher angle of attack (AoA)."
Lift is not just about AoA, it is about AoA and airspeed so I am sorry, but you were told the wrong thing. The inside wing stalls first because it is generates less lift (at the same AoA) as a result of moving slower then the outside wing.


text:
Why do spoilers seem to be slightly activated during take off?
In this video (minutes from 10:46 to 11:00), the spoilers seem to be slightly deployed during take off. What's the purpose of this? I've already seen this in other videos too.
I've also read the answers to the question When can spoilers be used on airliners, but they seem to be related to slowing down the aircraft or for descending faster. But what is the point during take off, when it's supposed the pilots want to climb and go faster?

possible duplicate of When can spoilers be used on airliners?

@reirab I agree it's a bit different but casey addresses this use of spoilers multiple times in his answer.

@fooot Oh, you're right. I somehow missed that part when I read over his answer.

Claudix, the slight deployment here is being done automatically as part of roll control (in conjunction with the ailerons.) See the end of casey's answer on the linked question for more detail.

That was exactly my doubt, @reirab! I also read about the roll control in the possible duplicated question, but what shocked me was the fact to activate the spoilers in a such slightly way. Thank you!

Yeah, when using them for roll control, the deflections are usually very slight. Spoilers are extremely effective at reducing the lift of a wing, so you don't want to deflect them too much in flight.

I'm voting to leave the question open, as I think if deserves its own answer, the duplicate being not very talkative about the use for roll control (e.g. why is it preferred to other surfaces). It seems the main reason is to increase the roll effect of the ailerons when flaps are extended (and more lift needs to be generated / countered to get the same amount of roll).

Funny that none of the three answers mentions yaw control. Ailerons give plenty of roll control already, but create adverse yaw. Spoilers should help to counteract this undesired yaw, which is worst at high lift coefficients.

Slightly off-topic, but pilots of some high-performance gliders take off with spoilers partially extended.  The reason is to direct more air outboard across the ailerons, increasing control authority at low speeds and decreasing the change of dragging a wingtip along the ground.

Spoilers lower lift and increase drag on the side where they are deployed. Symmetric spoiler deployment, therefore, is for slowing down. Asymmetric deployment not only creates a (small) rolling moment, but primarily a yawing moment which helps to counteract the adverse yaw created by ailerons, especially at the high lift coefficient at takeoff and early climb.
Spoiler deployment increases pressure ahead of the spoiler due to the slowing of local flow ahead of the obstruction caused by the spoiler, and it creates a local flow separation at and behind the spoiler, which in turn lowers the local pressure. Only the first effect lowers lift, but both create drag. The main effect of a limited spoiler deflection, therefore, is to increase drag.

Wouldn't the outboard spoilers be used for roll control? Because in the video two spoilers in the middle are slightly raised and the outer ones are not.

@JanHudec On this document (p.6) a scheme state only one spoiler per wing (out of5) is not used for roll control.

@ManuH: Yes, but it includes the outboard ones and in the video the outboard ones don't move. The video is 737 though and I don't have a reference for what that uses for roll control.

Just to add to (not disagree with) this answer: spoilers will occasionally be used in strongly gusting wind conditions to ensure the aircraft does not accidentally lift off the runway before reaching V1.

In this case, the flight spoilers are being used for roll control. Usually, the spoilers are used for roll control in concert with the ailerons, and are used during descent in order to slow down.
However spoilers are also used during take off in case of a cross wind.In that case, the pilot may want to reduce some lift in the upwind wing and employ spoilers instead of/along with the ailerons. A very small deflection in spoilers helps in increasing the drag over the wing and thus aid in roll control.
However, it is to be noted that the operation of spoilers during takeoff is very restricted in order to prevent flow separation.
In modern aircraft, the spoilers are used automatically with the ailerons. So, when the pilot operates the yoke, he is not consciously deciding to employ them, but rather the control system does it for him.

Large jet aircraft have multi function spoilers. They aide in turning the aircraft at low speed. When the aircraft needs to be slowed down in the air and on landing all of the spoilers are activated.

I agree with Eric.  Many business jets gave a spoiler on feature which aids the pilot with roll control.  Spoilerons are typically activated with a flaps below a preset level and aileron movement.
Spoilerons usually rise up when the aileron on the side rises.  Thus, they aid in rolling the airplane.
Most likely on takeoff the pilots are correcting for winds and the spoileron system is active.


text:
What are these long tubes under the wings?
I wonder what are the elements below the wings (pointed by the black arrows in the image). I'm not referring to the sticks at the end of them, which I found them to be "static wicks", used for static electricity discharge.

@Simon no he's explicitly not talking about the static wicks. But instead about the anti-shock bodies.

@Simon , as I pointed out in the post, I was not referring to static wicks but to the pods. Thank you ratchetfreak for your dup.

Doh, I'll delete the comment :)

They are flap track fairings which contain the flap mechanism.
They are called Küchemann carrots (also called anti-shock or Whitcomb body) and are used to reduce wave drag in transonic speeds.